This invention relates to a precombustion chamber construction of an internal combustion engine and more particularly to a precombustion chamber made of a ceramic material to improve the thermal efficiency of an engine and durability and heat-resistance of the precombustion chamber.
In order to improve the thermal efficiency of engines, particular characteristics of exhaust gases and the durability of precombustion chambers of internal combustion engines, particularly diesel engines, various attempts have been made to form part or all of turbulence chambers of internal combustion engines from ceramic materials, thereby utilizing their superior characteristics such as heat-resistance and thermal insulating capability.
However, because ceramic materials have thermal expansion coefficients which are smaller than those of materials constituting cylinder heads, for example, cast irons or aluminum alloys, supporting forces of the cylinder heads for the precombustion chambers tend to decrease when the cylinder heads are at high temperatures. With a precombustion chamber construction of a ceramic material consisting of upper and lower members, particularly, there is a tendency of the members to rotate relative to each other, so that an injection hole for communicating a main chamber with the precombustion chamber moves from its proper position to disturb normal ignition and explosion of a fuel. Moreover, when the upper and lower members rotate relative to each other to an extreme extent, a fuel injection nozzle and a glow-plug may be damaged by the movement.
To avoid the above undesirable effects Japanese Laid-open Utility Model Application No. 58-79,019, as shown in FIG. 1 herein, a precombustion chamber 10 is made in a two-split construction comprising an upper member 3 and a lower member 4, between which are inserted an annular gasket 6 and a thermal insulating spacer 7 made of heat-resistant metals so as to urge in their axial directions toward each other with the aid of an elastic force of the annular gasket 6, thereby forming a unitary body.
With this arrangement, however, the relative rotative movement of the upper and lower members 3 and 4 is prevented only by frictional forces between the annular gasket 6 and end faces of the upper and lower members 3 and 4. Accordingly, this arrangement does not solve the problem of damage to the fuel injection nozzle and glow-plugs sufficiently. Moreover, the requirement that the annular gasket and the thermal insulating spacer separate from the upper and lower members increases the numbers of parts, thereby making difficult the management of products and increasing the cost of the products.